This activity was designed for grades 4th thru 8th. Students will acquire a working definition of the word "displacement". Students will also understand that the volume (size) of an object placed in water affects the amount of water that is displaced.

Materials Needed:

Students will be in groups of 3-4 individuals. Each group should have the following items:

The 2 liter bottles are converted into overflow containers by taking a Phillips screw driver and heating the tip and using the tip to melt a hole into the container. The hole should be 3cm - 4cm from the top of the container. Next, place the 1/4" tubing into the hole, making sure to get a tight fit. The tubing allows for all the water from the container to flow into the graduated cylinder. * Note the water level should be at the point that water flows thru the tubing then stops. This level should be reached before performing exercises 2 thru 4.

Strategy:

Students will be introduced to the concept of displacement by observing the following exercise. Take two 2 liter containers filled 3/4 of the way with water. A 200 gram weight is placed in one of the containers of water and a 1,000 gram weight placed into the other container. Students should notice that the water levels have increased. Students should also notice that the container with the 1,000 gram weight has the higher water level. Students are then informed that, in each case, the change in water levels is a measure of displacement. Displacement is the amount of change in fluid volume from the initial point (beginning water level) to an ending point. Students are then asked to construct a definition of the word displacement based on their observations. Students are then asked to theorize as to what led to the different levels of displacement. Most students tend to theorize that the heavier objects' weight leads to a higher water level. Students are now ready to perform the following experiments to test their theories. Have students form groups of 3 or 4 individuals, so that each group will conduct the following experiments.

Experiment 1: Place the various weights (300, 800, and 1200 grams) into different identical containers and notice the change in water levels of the three containers. Once again, students should notice that the greater the weight in the container the higher the level of displacement. This observation may lead to the conclusion that the weight of an object affects the amount of water that a object displaces.

Experiment 2: On a balance scale have students weigh the two objects of the same weight but different sizes. Next, place each object into an overflow container and measure the amount of water displaced. Any object that floats should be held below the water level, until the (displaced) water empties into the graduated cylinder. Students should notice that the object with more volume (greater size) displaces more water. Students conclude that it is an objects' size that determines the amount of water displaced. To prove the findings of experiment 2, perform experiment 3.

Experiment 3: Place the two objects of similar volumes and different weights into the overflow containers. Students should notice that both objects displace similar amounts of water, which would substantiate the findings of experiment 2.

Experiment 4: Now place the 300 gram weight into the over flow cylinder and record the amount of water displaced. Next, hold an inverted styrofoam cup submerged under water and record the amount of water displaced. Once again, students shouldnotice that the cup displaces more water than its weight, further illustrating that it is the volume of an object that determines the amount of water that the object displaces.

Performance Assessment:

Students will receive a maximum of 20 points for each experiment completed. A two question essay (20 points) will also be administered. A maximum of 100 points is possible. 100-90 = A 89-80 = B 79-70 = C 69-50 = D 49-20 = F 19-0 = 0